Most notable is TTN, an enormous scaffolding protein of the sarcomere, which contributes the most cases of DCM.28,29 For HCM and ARVC, TTN was classified as limited.14LMNA, encoding a protein of the inner nuclear membrane that exhibits striking pleiotropic effects in skeletal muscle, adipose, and other tissues, was considered definitive for DCM but limited for ARVC. The gene discussed is TTN; the disease is arrhythmogenic right ventricular cardiomyopathy.